The invention relates to a hydraulic controller for an automatic transmission of a motor vehicle.
German patent document DE 10 2005 031 066 A1 describes an automatic transmission having a hydraulic controller for a motor vehicle. The automatic transmission has a gear shifting system for shifting an engaged gear of the automatic transmission, the gear shifting system includes at least one gear shift piston-cylinder unit with a gear shift piston for actuating a shifting element in the form of a multi-plate clutch, and a gear shift pressure chamber in which an actuating pressure may be built up by supplying operating fluid. In addition, the gear shift piston-cylinder unit has a centrifugal oil chamber, in the form of a pressure compensation chamber, which is separated from the gear shift pressure chamber by the gear shift piston. The centrifugal oil chamber may be supplied with operating fluid via a centrifugal oil line which is provided by a first supply line.
In a rotating pressure chamber, centrifugal forces act on the operating fluid present therein and cause a pressure rise in the pressure chamber. The pressure rise is thus a function of the rotational speed at which the pressure chamber rotates. The effective pressure in the pressure chamber is therefore greater than the controlled, and thus intended, pressure. If operating fluid is likewise present in a centrifugal oil chamber located on the opposite side of the piston with respect to the pressure chamber, centrifugal forces act on this operating fluid, likewise resulting in a pressure rise at that location. Since the pressure chamber and the centrifugal oil chamber rotate at the same rotational speed, the pressure rise in the pressure chamber and in the centrifugal oil chamber is the same, so that they cancel one another out. When the centrifugal oil compensation is functioning, the controlled pressure thus agrees very well with the actual pressure in the pressure chamber, thus allowing precise control of the shifting element. If the centrifugal oil compensation is not functioning properly, in particular due to insufficient operating fluid in the centrifugal oil chamber, the actual pressure in the pressure chamber is greater than the controlled pressure. The shifting element may then possibly transmit a higher torque than desired, which may result in uncomfortable shifting. As the result of improperly functioning centrifugal oil compensation, the shifting element may unintentionally automatically engage, at least partially, due to the pressure rise in the pressure chamber.
Accordingly, exemplary embodiments of the present invention are directed to a hydraulic controller for an automatic transmission of a motor vehicle in which the shifting elements are precisely controllable.
According to exemplary embodiments of the invention, the hydraulic controller has a second supply line for supplying operating fluid to the centrifugal oil line, and thus to the centrifugal oil chamber. The second supply line may be closed and opened by means of a centrifugal oil valve. Thus, in situations in which functioning centrifugal oil compensation is necessary for the precise control of the shifting element, by opening the second centrifugal oil line, the centrifugal oil chamber may be rapidly supplied with operating fluid, and therefore the centrifugal oil chamber may be rapidly filled to a sufficient degree.
The centrifugal oil line is connected to multiple centrifugal oil chambers of multiple shifting elements, in particular multi-plate clutches of the automatic transmission. When reference is made to a centrifugal oil dome below, multiple, or all, centrifugal oil domes of the automatic transmission may also be intended.
The invention is advantageously usable when it may be ensured via suitable measures that the gear shift pressure chamber is always filled with operating fluid. In this case, the risk of the shifting element unintentionally engaging is particularly high. An example of one possible measure is to provide a valve in a discharge outlet of the gear shift pressure chamber that closes the connection to a tank below a definable pressure, for example having a level of 0.2 to 0.4 bar. Thus, in the normal case the pressure in the gear shift pressure chamber does not drop below the definable pressure. Another option is to control a minimum pressure in the gear shift pressure chamber, even when the shifting element is supposed to be disengaged. The mentioned definable pressure and the minimum pressure are selected in such a way that that the shifting element is still reliably completely disengaged when this pressure is applied in the gear shift pressure chamber.
The automatic transmission is designed, for example, as a transmission having multiple coupled planetary sets, and is designed in particular as an automatic transmission corresponding to German patent document DE 10 2008 055 626 A1 by the assignee of the present application. However, the automatic transmission may also be designed, for example, as an automatic gearwheel change transmission, as a dual-clutch transmission, or as a continuously variable transmission.
In one embodiment of the invention, the centrifugal oil valve is designed as a controllable valve, which in a normal position, closes the second supply line. The centrifugal oil valve is designed as a slide valve on the slider of which a control pressure and an elastic force act. In the normal position, in which no control pressure acts on the centrifugal oil valve, the spring presses the slider into a position in which it closes the second supply line. Simple control of the centrifugal oil valve is possible in this way. The control pressure is set, for example, by a pilot valve. The pilot valve is designed, for example, as a solenoid control valve, in particular as a so-called direct control valve. The pilot valve is supplied with a supply pressure, for example in the form of a working pressure or a valve supply pressure, from which the pilot valve derives a desired pilot pressure corresponding to the control by an electronic transmission controller.
In one embodiment of the invention, hydraulic elements for setting flow rates of the operating fluid are situated in the first and/or the second supply line. The mentioned hydraulic elements are designed as throttles. Flow rates of the operating fluid in the first and second supply lines may advantageously be influenced and set using the mentioned hydraulic elements. It may thus be ensured that an excessive amount of operating fluid does not flow via the second supply line to the centrifugal oil chamber, so that the first supply line, and thus components that are supplied by the first supply line, are undersupplied.
In one embodiment of the invention, the first supply line is connected to the centrifugal oil valve via two connections or sections. One of the connections or a section may be blocked by means of the centrifugal oil valve so that no operating fluid is able to flow into the first supply line via this connection or this section. The one connection or section is blocked in particular when the centrifugal oil valve opens the second supply line. The flow rate and the pressure in the first supply line may thus be changed by the centrifugal oil valve.
This is particularly important when, due to multi-purpose use of the control pressure for the centrifugal oil valve together with control of the centrifugal oil valve, a pressure upstream from the centrifugal oil valve is increased at the same time, and a component, for example a hydrodynamic torque converter, whose supply pressure is not allowed to exceed a pressure limit is situated in the first supply line. In this case, a throttle on the centrifugal oil valve may be situated in the non-blockable connection of the first supply line, by means of which the pressure in the first supply line may be limited when the pressure upstream from the centrifugal oil valve increases.
The invention is advantageously usable when a hydrodynamic torque converter and/or a transmission fluid cooler and/or branches in lubricating oil lines is/are situated in the first supply line. Components of the automatic transmission, such as plates of multi-plate clutches, gearwheels, or bearings are lubricated and/or cooled via the lubricating oil lines.
In one embodiment of the invention, the hydraulic controller has a pilot valve and a first and a third valve unit. A pilot pressure set by means of the pilot valve is conductable as control pressure to the first and third valve units and to the centrifugal oil valve as the second valve unit. By means of a counterpressure line, a counterpressure acting against the control pressure may be applied to the third valve unit, and actuation of the third valve unit may thus be prevented.
The valve units are designed as slide valves, for example as shift valves or control slide valves.
An actuation of the third valve unit is understood to mean a change in a switch position of the third valve unit or a change in a pressure or flow rate set by the third valve unit.
The third valve unit is designed as a shift valve, on the slider of which the pilot pressure may act as control pressure on one side, and the counterpressure may act on an opposite side of the slider. In addition, the third valve unit has a spring that is able to apply a force on the slider which acts against the pilot pressure. By an appropriate design of the effective surfaces on the slider, the pressure ranges of the pilot pressure and the counterpressure, and optionally the spring, it may be ensured that an actuation of the valve unit may be prevented by applying a counterpressure to the third valve unit. In this case, an actuation of the valve unit is understood to mean the change in the switch position of the switching valve.
In one embodiment of the invention, for actuating the first valve unit, in each case a first, second, and third pressure range is provided to the centrifugal oil valve as the second valve unit, and to the third valve unit. In this regard, a switching valve is understood to mean that changes in the state or the behavior of the switching valve result from changes in the control pressure within the pressure range associated with the switching valve. A change in the switch position of the shift valve is achieved due to a change in the control pressure from one limit to another limit of the pressure range. An increase of the control pressure above an upper limit, or a decrease below a lower limit, of the particular associated pressure range then has no further effect on the switch position of the shift valve. For a valve unit designed as a control slide valve, the adjusted pressure or the flow rate changes in the event of changes within the pressure range. However, it is also possible for the control pressure to still have an influence on the adjusted pressure or the flow rate for the case in which the control pressure is outside the associated pressure range. The pressure ranges may overlap, but it is also possible for there to be a range in each case between the pressure ranges that is not associated with any of the pressure ranges. The first, second, and third pressure ranges are present one after the other in the order of increasing pressure. For example, a pressure range of approximately 0 to 3 bar is associated with the first valve unit, a pressure range of 4 to 5 bar is associated with the centrifugal oil valve, and a pressure range of 6 to 8 bar is associated with the third valve unit.
Due to the counterpressure on the third valve unit, an actuation of the third valve unit during an intentional actuation of the centrifugal oil valve may be reliably avoided. In fact, this should not occur at all on account of the distribution of the pressure ranges. However, component tolerances or wear or aging of the hydraulic components may result in shifting and/or overlapping of the pressure ranges, and thus, unintentional actuation of the third valve unit. Reliable operation of the hydraulic controller may be made possible by applying the counterpressure to the third valve unit.
However, it is also possible for the third pressure range to be present between the first and the second pressure range. For example, a pressure range of approximately 0 to 3 bar is associated with the first valve unit, a pressure range of 4 to 5 bar is associated with the third valve unit, and a pressure range of 6 to 8 bar is associated with the centrifugal oil valve.
As a result of preventing the actuation of the third valve unit due to the counterpressure, the first or second valve unit may be controlled without the control having effects on the third valve unit. In the mentioned example, the centrifugal oil valve may be controlled without the third valve unit being actuated. The centrifugal oil valve and the third valve unit may thus be independently controlled by only one pilot valve.
In one embodiment of the invention, the counterpressure that may act on the third valve unit, against the control pressure, is derived from a pressure that primarily performs some other function. The term “primarily performs some other function” should be understood to mean that this pressure is not primarily set for deriving the counterpressure therefrom. The mentioned pressure is set, for example, in order to control a further valve unit, or in particular to actuate a shifting element of the automatic transmission, for example in the form of a multi-plate clutch or multi-plate brake. The pressure from which the counterpressure is derived is selected in such a way that in situations in which control of the centrifugal oil valve is meaningful or necessary, the counterpressure is high enough to prevent unintentional actuation of the third valve unit.
In one embodiment of the invention, the hydraulic controller has a shuttle valve by means of which the counterpressure may be derived from a first pressure or from a second pressure. The shuttle valve is designed as an automatically switching valve that derives the counterpressure from the higher of the two mentioned pressures. The shuttle valve is designed as a ball shuttle valve. The actuation of the third valve unit may thus be prevented not only as a function of one pressure, but, rather, as a function of two pressures. Thus, control of the second valve unit without effects on the third valve unit is possible in very many situations.
In one embodiment of the invention, the counterpressure is derived from a pressure of an actuating system of a shifting element of the automatic transmission. The control of the centrifugal oil valve may thus be made possible without effects on the third valve unit when the automatic transmission is engaged in certain gears, and thus, when certain shifting elements are actuated. The rapid filling of one or more centrifugal oil domes is usually necessary only for certain shifting operations within the automatic transmission. Which shifting operations are affected depends on the design of the automatic transmission. For example, there may be shifting in which a shifting element in the form of a multi-plate clutch is accelerated very strongly, but must remain engaged. If the centrifugal oil dome is not sufficiently filled, as described above this may result in unintentional engagement of the shifting element. If the counterpressure is derived from an actuating pressure of a shifting element, gears may be determined in which control of the centrifugal oil valve is possible without actuating the third valve unit. If an above-described shuttle valve which may switch between two actuating pressures of two different shifting elements is additionally used, a sufficiently high actuating pressure is available in a plurality of gears.
The invention is advantageously usable when the first valve unit is provided for setting a lubricant pressure, and the third valve unit is associated with a parking lock actuating system.
The first valve unit is designed in such a way that an increase in control pressure causes an increase in lubricant pressure. In the above-mentioned example of the pressure ranges associated with the valve units, this means that a high lubricant pressure is set for controlling the parking lock actuating system or the centrifugal oil valve.
A parking lock of the parking lock actuating system must be actuated, in particular engaged, only when the automatic transmission is not in gear. Therefore, this does not represent any functional limitation for the parking lock actuating system when actuation of the parking lock is not possible in some gears on account of the counterpressure. On the other hand, filling of the centrifugal oil domes is necessary only when the automatic transmission is engaged in certain gears. The parking lock is actuated only when the automatic transmission is not in gear. Thus, the centrifugal oil valve may be controlled in all necessary situations. Actuation of the parking lock actuating system and of the centrifugal oil valve by a shared solenoid control valve does not limit the functionalities of the two systems.
Further advantages, features, and particulars of the invention result from the following description of exemplary embodiments and with reference to the drawings, in which identical or functionally equivalent elements are provided with identical reference numerals.